Three dimensional structure of the distal condyles of the third metacarpal bone of the horse.

This research investigates the three-dimensional structure of the part of the horse’s third metacarpal bone that is often involved with distal condylar fractures.

Overview of the Research

The study delved into the intricate examination of the third metacarpal bone (McIII) of horses, predominantly the areas commonly associated with distal condylar fractures. The study was conducted using limbs obtained from Thoroughbred horses spanning different ages, destroyed due to varied reasons from incurable fractures to other conditions. The methods of the study involved cutting beams, blocks, and sections along the primary axes, embedding them in PMMA, and some tested without embedding.

Methods of Examination

• The examination techniques included conventional and confocal optical microscopy, scanning electron microscopy (SEM), and radiography. These diverse tools provided varying scales of resolution and depth evaluation which were crucial for the 3D examination of the bone structure.

Findings

• The research found that the mineralised articular cartilage, a crucial component of the joint, tends to split in the sagittal plane. This is the anatomical direction along the body’s midline, splitting the body into left and right halves.
• The main support structures or ‘trabeculae’ proximal to the subchondral bone, a layer of bone beneath the cartilage, were observed to be sturdy plates running in the sagittal direction.
• Conversely, the medial-lateral connections appeared to be less significant. These trabeculae contained small blood vessel canals, further emphasizing the importance of this bone’s structure in providing necessary nutrients for bone health and integrity.
• The sagittal structure was found to provide maximum strength and protection in the plane of the bone’s rotation, but ironically provides minimal resistance to fractures propagating in this same plane.

Conclusion

• As a result, the researchers were able to connect the common paths of distal condylar fractures in the horse’s third metacarpal bones with the anisotropic structural features of the mineralised tissues, providing an explanation rooted in the bone’s unique microarchitecture.